I think that IntelligenceExplosion is just a portal to make further research easier (by collecting links and references, etc), while Facing The Singularity is lukeprog actually explaining stuff (from the Preface):

I’ve been trying to answer those questions in a long series of brief, carefully written, and well-referenced articles, but such articles take a long time to write. It’s much easier to write long, chatty, unreferenced articles.

Facing the Singularity is my new attempt to rush through explaining as much material as possible. I won’t optimize my prose, I won’t hunt down references, and I won’t try to be brief. I’ll just write, quickly.